In a chain drive mechanism of a motorcycle, when a chain which runs from a driven sprocket side meshes with a driving sprocket so as to be fed, the chain being somewhat, under tension is so quickly meshed with the teeth of the sprocket that a collision sound is generated. Since such collision is made between metal materials, the collision sound consists mostly of a high frequency component, and is called chain drive noise of the motorcycle, which is desired to be reduced.
In the sprocket on the driven side, the links of the chain on the relaxed side are meshed in turn according to the feed of the chain. However, immediately before this meshing, a clearance is formed between the chain and sprocket due to the relaxation of the chain. From this state, the chain collides suddenly with the teeth of the sprocket to thereby generate noises which are also called chain noise.
In conventional chain drive mechanisms as in a motorcycle or the like, such noises of collisions are generated on both the driving side and driven side due to the tension and relaxation of the chain when the chain meshes with the teeth of the sprocket.
Heretofore, as a means for preventing such chain noises, there has been proposed a means in which rubber or the like is provided on a sprocket by means, such a baking, so that the chain noises may be reduced by the cushioning action of the rubber. In such conventional means, because it is necessary to bake and fit rubber to the sprocket, there are disadvantages with respect to productivity and high cost. Also, because the rubber becomes integral with the sprocket, it will be compressed and deformed due to the driving force of the chain, and will be fatigued and worn early by the high temperature of friction heat generated between the chain and sprocket and by operation for a long time. Thus, there is difficulty with respect to durability, and lack of preventing noises.